Corrugated sheet metal roof paneling has been considerably improved over the years and is now recognized as a good economical and practical roofing material.
In general, the roofing panels are rolled from sheet metal in corrugated form and lengths sufficient to extend from the ridge of the roof being constructed to the eaves. And, next adjacent panels are made to overlap each other and to be locked together in some manner and thereby provide a wide expansive roof covering.
One well recognized and accepted system, which is known as the standing seam ROOF-LOK system, is offered by Architectural Panels, Inc. of Pontiac, Mich., and makes use of upturned edges on the next adjacent panels which interfit and are so formed that they lock together, with the use of a motorized seaming tool, to provide what is known in the trade as a "rib lock" arrangement.
Of particular note in this system is the manner in which the roof panels are fastened to the roof supporting structure.
This is accomplished by the use of a fastener or clip that is received between two next adjacent roof panels, at spaced intervals along their length, and which is itself formed to interfit between the two panel edges in the course of having them seal rolled together. The fastener or clip is also formed to include a lower end, that extends below the plane of the roof panels, and which is turned back on itself to provide a hook or catch that can be engaged with the roof supporting structure or to other receptive means fastened to the roof supporting structure.
Presently, and in the structure disclosed hereinafter, a receptive or so-called base member is used that has an elongated opening formed centrally therewithin and which is provided with an overturned edge that serves as a complimentary hook or catch for the lower end of the fastener or clip to be engaged with it. And, with the fastener or clip allowed relative movement in the elongated opening and on the base member during the relative expansion and contraction of the roof panels due to temperature changes. Accordingly, with the base member fastened to the roof supporting structure, the fastener or clip engaged to the base member and also in seam locked engagement between next adjacent roof panels, the panels themselves are retained and held on the roof supporting structure.
By making the receptive hook or catch that is provided on the base member longer in length than the width of the hook or catch on the lower end of the fastener or clip, the fastener or clip is allowed the relative movement mentioned which in turn allows for the eave-to-ridge expansion and contraction of the roof panels.
Although this system works very well, there is friction and wear that occurs between the roof panels and the base member that the fastener or clip is engaged to. And, since the roof panel expansion for a hundred foot length, with a temperature variation of 100 degrees, will be a much as 1.6 inches, it can be appreciated that there is a significant amount of relative movement that can occur with large expansive roofs and where the friction and wear between the roof panels and the means provided to retain them on their supporting structure could have serious consequences.